Partially reinforced hollow profile

ABSTRACT

A method for producing partially reinforced hollow profiles made of a metal, particularly steel, or a steel alloy includes forming a blank, together with a plurality of reinforcing metal elements arranged on the blank, into a hollow profile using the rolling-in technique or by means of U-O forming, wherein after forming the reinforcing elements arranged on the blank are connected to the formed blank at least by means of a positive interengagement. This method provides a simple and cost-effective procedure for producing reinforced hollow profiles made of metal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Phase Application of International Application No. PCT/EP2008/059930, filed on Jul. 29, 2008, which claims the benefit of and priority to German patent application no. DE 10 2007 038 713.1-14, filed on Aug. 14, 2007. The disclosures of the above applications are incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

The invention relates to a method for producing partly reinforced hollow profiles from a metal, in particular from steel or a steel alloy.

BACKGROUND

Partly reinforced hollow profiles are used particularly in the body structures of motor vehicles but also in other technical fields to enable a certain strength to be achieved at the same time as minimal weight. Hollow profiles of this kind, and in particular tubes, can be produced in the form of so-called “tailored tubes” which comprise tubes of different wall thicknesses and/or made of different materials which are welded together. In this way, the component so produced is able for example to absorb and transmit higher forces at points of greater wall thickness. In the regions where it is permissible for the stiffness of the component to be relatively small on the other hand, the wall thickness is reduced to the minimum size required, thus keeping the weight of the component low.

A problem with these modular tubes is that they are relatively expensive to produce. Particularly where there are a large number of necessary reinforced regions, the result is a large number of tubes which have to be welded together orbitally. The same is of course also true for hollow profiles of other shapes made from tailored blanks.

To simplify this process, it is known from German patent application DE 102 21 880 A1 for reinforcing members which wholly or partly surround a tube to be slid onto the tube requiring reinforcement and then to be formed by an internal high pressure process in such a way that the partial reinforcing members have a positively interengaged connection to the tube. However, given the capital cost of the equipment and tools needed, the internal high pressure forming process is expensive and the production costs for a partly reinforced tube are thus relatively high. As well as this, what is also known from the prior art, from DE 198 19 484 A1, is for a blank to have a reinforcement arranged on it before the forming process, and for the blank to be provided with this reinforcement while it is being deep drawn into a U-shaped profile. Finally, in the production of partly reinforced semi-finished products, it is known from DE 197 37 969 A1 for the reinforcing members to be connected to the as yet unformed semi-finished products by a solid joint. The production of a solid joint between reinforcing member and as yet unformed semi-finished product on the one hand requires a great deal of work to be done and on the other hand results in stresses in the semi-finished product when it is subsequently formed.

SUMMARY OF THE INVENTION

Taking the above as a point of departure, an aspect of the present invention is to propose a simple and inexpensive method for producing partly reinforced hollow profiles from a metal.

In accordance with a first teaching of the present invention, the aspect as derived above is achieved by virtue of the fact that a blank, having a plurality of metal reinforcing members arranged on the blank, is formed into a hollow profile by using the rolling-in technique or by U-to-O forming, the reinforcing members arranged on the blank being, after the forming, in a state where they are connected to the formed blank by positive interengagement, the preference being for a connection to be made only by positive interengagement.

Surprisingly, it has been found that blanks having reinforcing members arranged on them can be shaped, together with the blank, even by the rolling-in technique or by U-to-O forming, a positive interengagement between the reinforcing members and the blank being obtained at the same time. The advantages of the method according to the invention become apparent particularly when a plurality or a large number of reinforcing members are provided on the hollow member because these are connected at the same time to the formed blank by the positive interengagement. In U-to-O forming, a flat blank is shaped into a preform together with the reinforcing members arranged on the blank, is formed into a closed hollow profile in a die and then welded. The preform may for example be V-shaped or U-shaped in cross-section. The possibility does, however, also exist of cross-sectional shapes of a different kind being provided for the preform. When the rolling-in technique is being performed, a blank is placed in a die together with the reinforcing members arranged on the blank and the die forms the hollow profile from the flat blank having the reinforcing members arranged on it. When this happens, and provided that a shaped core is used, the blank slides in a slit region between the shaped core and the die until the edges of the blank are situated opposite one another to be welded. If the reinforcing members are situated on the inside, the rolling-in technique can be performed with the shaped core, which means that the shaped core causes the reinforcing members to be impressed into connection with the blank. If the reinforcing members are situated on the outside, it is also possible, in principle, for the rolling-in technique to be performed without a shaped core. By using the method according to the invention, it is therefore possible for equipment which already exists to be used for producing partly reinforced hollow profiles, which means that the capital costs are low. Also, the method according to the invention is characterized by short cycle times, which also contribute to making the method highly economical. Finally, the stress on the material during the U-to-O forming and during the rolling-in technique is particularly low, which means that further forming operations on the hollow profile produced are also possible.

In a first embodiment of the present invention, a good match to the intended purpose of the partly reinforced hollow profile is achieved in that the reinforcing members have wall-thicknesses which are matched to the stress. The different wall-thicknesses are able to make allowance for regions of the hollow profile which are more and/or less severely stressed. By selecting and arranging different reinforcing members on the blank, the method according to the invention makes it possible, at no major expense, for partly reinforced hollow profiles properly designed for the stress to be produced which can also easily have a large number of reinforced regions.

As well as having different wall-thicknesses, the reinforcing members may also be composed of materials which are matched to the stress. For example, different steel alloys can be used. The advantage of this embodiment lies in the fact that materials which are not weldable can also be used, because the reinforcing members are connected to the formed blank by the positive interengagement.

By the method according to the invention, it is also possible for a response to be made to stresses implied by the intended purpose by arranging the reinforcing members on the inside and/or the outside of the hollow profile. As has already been stated above, reinforcing members arranged on the inside call for the use of an internal shaped core when the rolling-in technique is being used or when U-to-O forming is being performed to cause the stiffening members to be impressed into connection with the blank forming the hollow profile.

In a next, refined, embodiment of the method according to the invention, a closed hollow profile can be provided by welding the opposing edges of the formed blank together by a longitudinal seam.

If a partly reinforced tubular hollow profile of circular cross-section is produced, a partly reinforced hollow profile which is particularly easy to form can be provided. A partly reinforced hollow profile produced in this way can for example be used as a starting product for the production of other, more complex, hollow profiles.

To enable the method for production to be further simplified, the reinforcing members are preferably fixed in place and/or positioned on the blank before the forming. What “fixing in place” means for the purposes of the present invention is that the reinforcing members are merely secured against slipping during the forming. This can be done on the one hand by the shape of the die itself, but on the other hand what may also be used for the fixing in place are tack welds and/or spots of adhesive-bonding or a slight positive interengagement achieved by forming the blank and the reinforcing members, for example into a folded-together U-shape. Positioning can also take place on the blanks. As compared with the “solid” connection of the reinforcing members to the blank to be formed, which connection is known from the prior art, the cost and complication of the work is considerably less.

In a refined embodiment of the method according to the invention, the reinforcing members may be secured against slipping axially by, in addition, firmly bonding the reinforcing members to the blank, after the forming, by tack welds or weld seams and/or spots of adhesive-bonding.

Additional fixing in place of a particularly simple kind of at least one reinforcing member can be achieved by causing at least one reinforcing member to surround the circumference of the hollow profile and causing it to be welded together at the opposing edges after the forming.

Finally, a further improvement can be made to the method according to the invention by incorporating further functional elements in the hollow profile, during the forming, by embossing, punching and/or shaping. This makes a further reduction in the number of steps of operation needed to produce a corresponding hollow profile, thus enabling the production costs too to be brought down. What may be incorporated in the hollow profiles as functional elements are for example impressions or embossings and/or holes but also flanges.

BRIEF DESCRIPTION OF THE DRAWINGS

There are many possible ways in which the method according to the invention can be embodied. In this connection, attention is directed to the illustrative and non-limiting description of embodiments which is given by reference to the drawings. In the drawings:

FIG. 1 is a view in section of an embodiment of a blank having reinforcing members arranged thereon, before forming.

FIG. 2 is also a view in section, of one half of a hollow profile after a blank as shown in FIG. 1 has been formed into a tube according to one embodiment of method according to the invention.

FIG. 3 shows an embodiment of a pre-formed blank for fixing the reinforcing members in place.

FIGS. 4 a and 4 b are schematic axial views in plan of an apparatus for carrying out the method according to the invention, at two different points in time.

FIG. 5 is a schematic axial view in plan of an apparatus for carrying out the rolling-in technique with a shaped core by means of a further embodiment of the method according to the invention.

FIG. 6 is a schematic view in plan of an apparatus for carrying out the rolling-in technique without a shaped core according to a final embodiment of method according to the invention.

DETAILED DESCRIPTION

Shown in FIG. 1, in a view in section, is a blank 1 having reinforcing members 2′, 2″, 2′″ arranged thereon, in the unformed state. The reinforcing members 2′, 2″, 2′″, which are also referred to as patches, are either not fixed in place (2′) or are fixed by means of tack welds or spot of solder or brazing 3 or a layer of adhesive 4 against slipping on the blank 1. The layer of adhesive 4 may also take the form of a spot of adhesive-bonding. The purpose of the fixings effected by means of the tack weld or the spot of solder or brazing 3 and the layer of adhesive 4 or the spot of adhesive-bonding is merely to protect the reinforcing members against slipping, when for example the blank is being placed in the apparatus for forming. There is no need for a solid connection between blank and reinforcing member. After the forming, performed for example by the use of the rolling-in technique or by U-to-O forming, the reinforcing members 2′, 2″, 2′″ are impressed into connection with the formed blank 1, and a positive interengagement is thus made between formed blank 1 and reinforcing members 2′, 2″, 2′″. The positive interengagement is enough to permanently connect the reinforcing members 2′, 2″, 2′″ to the formed blank.

A further possible way of holding the reinforcing members 2 in position on the blank 1 is shown in FIG. 3 in a schematic section through the pre-formed blank 1. The pre-formed blank 1 has been formed into a V, on which the reinforcing member 2 is arranged in positive interengagement and/or by non-positive fit. The preform which is produced in this way may be formed into a closed hollow body by, for example, a U-to-O method of forming. This is what is shown in FIGS. 4 a and 4 b in a schematic axial plan view of an apparatus 5 for carrying out U-to-O forming.

An apparatus 5 for carrying out U-to-O forming comprises a die which may for example consist of two die-halves 6, 7. In the closed-together state, the die-halves 6, 7 form the shape of the hollow profile to be produced. The blank 1 is placed in the die-half 7 with the reinforcing members 2 arranged on the blank 1, which are indicated in the present case only by a dotted line, and the die-halves 6 and 7 are then closed together. As the closing-together takes place, the blank 1 and the reinforcing members 2 are formed into a closed hollow profile, as shown in FIG. 4 b. After the forming, the reinforcing members 2, which are situated on the outside, have been impressed into connection with the blank 1 in the way which has already been shown in FIG. 2, and they are thus connected to the blank forming the hollow profile by positive interengagement. The opposing edges of the blank and the reinforcing members can then be welded together, by means for welding which are not shown in the drawings, thus enabling a closed hollow profile to be produced.

Although what is shown in FIGS. 4 a and 4 b is a method of performing U-to-O forming where the reinforcing members 2 are situated on the outside, it is also easy to imagine reinforcing members 2 situated on the inside being used, though in this case a shaped core is used to impress the reinforcing members situated on the inside in a similar way to what happens in the rolling-in technique which is described below.

An embodiment of an apparatus for performing the rolling-in technique when using reinforcing members situated on the inside is shown in a schematic plan view in FIG. 5. The die of the apparatus shown in FIG. 5 comprises two die-halves 8, 9. The blank 1, with the reinforcing members 2 arranged thereon, is placed between the die-halves 9 and 8. Provided in addition is a shaped core 10 which, when the die-halves 8, 9 are closed together, causes the reinforcing members 2 situated on the inside to be impressed into connection with the blank 1. As an option, a blade 11 may be provided which extends in the axial direction of the hollow profile to be produced and which serves to produce a gap at the joint between the opposing edges of the formed blank 1. Once the blank has been formed, the hollow profile which has been produced in this way can be easily welded together by a reliable process by a longitudinal seam.

Finally, FIG. 6 shows an apparatus for performing the rolling-in technique without a shaped core, with the reinforcing members 2 being provided on the outside of the hollow profile which is produced later. If, however, reinforcing members 2 situated both on the inside and the outside are to be formed together with the blank 1, it is necessary for a shaped core 10 to be used.

The apparatus described above for carrying out the method according to the invention are apparatus of conventional and relatively simple construction which result in low capital costs. As a result, with the method according to the invention, both when using U-to-O forming and when using the rolling-in technique, partly reinforced hollow profiles, and in particular ones having a plurality of reinforced regions, can be inexpensively produced. 

1. Method for producing partly reinforced hollow profiles from a metal, the method comprising forming a blank, together with a plurality of metal reinforcing members arranged on the blank, into a hollow profile by using the rolling-in technique or by U-to-O forming, the reinforcing members arranged on the blank being, after the forming, in a state where they are connected to the formed blank by positive interengagement.
 2. Method according to claim 1, wherein the plurality of reinforcing members have wall thicknesses which are matched to the stress.
 3. Method according to claim 1, wherein the plurality of reinforcing members are composed of materials which are matched to the stress.
 4. Method according to claim 1, wherein the plurality of reinforcing members are arranged on the inside and/or the outside of the hollow profile.
 5. Method according to claim 1, wherein opposing edges of the blank after forming are welded together by a longitudinal seam.
 6. Method according to claim 1, wherein a partly reinforced tubular hollow profile of circular cross-section is produced.
 7. Method according to claim 1, wherein the plurality of reinforcing members are fixed in place and/or positioned on the blank before the forming.
 8. Method according to claim 1, wherein after the forming the plurality of reinforcing members are, in addition, firmly bonded to the blank by tack welds, weld seams and/or spots of adhesive-bonding.
 9. Method according to claim 1, wherein at least one of the plurality of reinforcing members surrounds a circumference of the hollow profile and is welded together at opposing edges after the forming.
 10. Method according to claim 1, wherein further functional elements are incorporated in the hollow profile, during the forming, by embossing, punching and/or shaping. 